The copolymerization of styrene and .alpha.-olefins is usually very difficult in the direct copolymerization processes using Ziegler-Natta catalysts (see Aaltonen, et al., Macromolecules 27, 3136, 1994 and Soga et al., Macromolecules, 22, 2875, 1989). Especially involving stereospecific heterogeneous catalysts, the reactivity of monomer is sterically controlled, the larger the size the lower the reactivity. Only very few % of styrene has been randomly incorporated in polyethylene (HDPE) and isotactic polypropylene (i-PP) in the batch reactions. By using several low reactivity metal oxide catalysts and tinder very inconvenient "living" polymerization conditions, the combination of Ziegler-Natta polymerization and transformation reactions has been reported to produce some .alpha.-olefin/styrene diblock copolymers (see Doe et al., "Coordination Polymerization","Living" Coordination Polymerization of Propylene and its Application to Block Copolymer Synthesis, pages 249-265, edited by Price and Vandenberg, Plenum Press, 1983).
On the other hand, the copolymerization of styrene (styrene derivatives) and isobutylene with cationic catalysts is known in the art (see Harris et al., U.S. Pat. No. 4,145,190 and Macromolecules, 19, 2903, 1986). Under cationic polymerization conditions, p-alkylstyrene and isobutylene have been copolymerized rather readily to yield copolymers covering a wide compositional range. Thus, such copolymers ranging from tough, glassy high poly(p-alkylstyrene) content copolymers for use in plastic blends, to rubbery p-alkylstyrene incorporated isobutylene copolymers have been prepared. Furthermore, the copolymers have been used in a variety of applications, including use as adhesives in connection with other materials taking advantage of the surface characteristics of the polyisobutylene sequences, as coatings, as asphalt blends, and in various plastic blends.
The interest of incorporating p-alkylstyrene in polymers is due to its versatility to access a broad range of functional groups. The benzylic protons are ready for many chemical reactions which introduce functional groups at the benzylic position under mild reaction conditions. The oxidation of alkylbenzene to carboxylic acids has been widely studied (see Onopchenkov et al., J. Org. Chem. 37, 1414, 1972 and Ferrari, et al., Macromolecules, 24, 6340, 1991). The halogenation of benzylic systems is also a well-established chemistry (see Mohanraj, et al., Macromolecules, 19, 2470, 1986; Pini, et al., Macromolecules, 20, 58, 1987, Jones et al., Polymer, 31, 1519, 1990). Some reports have also shown the effective metallation reactions to form a benzylic anion in alkylbenzene species (see Nagasaki, eta al., Makromol. Chem., Rapid Commun., 7, 437, 1986 and Bonaccorsi, Roggero et al., Polymer International, 30, 93, 1993). In addition, the further conversion of halogenated and metallated products significantly broaden the scope of functional groups in polymers to almost all the desirable organic functional groups. The benzylic halogen functionality constitutes a very active electrophile that can be converted to many other functionalities via nucleophilic substitution reactions. This functionalization route has long been recognized and the chemical literature is replete with examples of these reactions. "Clean" conversions in high yield to many functionalities, including the following have been reported: aldehyde, carboxy, amide, ether, ester, thioester, thioether, alkoxy, cyanomethyl, hydroxymethyl, thiomethyl, aminomethyl, cationic ionomers (guaternary ammonium or phosponium, s-isothiouronium, or sufonium salts), anionic ionomers (sulfonate and carboxylate salts), etc. In addition, the literature describes many examples in which a benzylic halogen is replaced by a cluster of other functionalities by nucleophilic substitution with a multifunctional nucleophile such as: triethanol amine, ethylene polyamines, malonates, etc. Nearly all of this previous work has been with simple, small (i.e. non-polymeric) molecules containing an aromatic halomethyl (or benzylic) functionality. However, a considerable amount of art also exists on nucleophilic substitution reactions involving chloromethyl styrene and polystyrenes containing aromatic chloromethyl groups to introduce other functionalities. Much of this work involves reactions with "styragels", or lightly cross-linked polystyrenes containing various amounts of benzylic chlorine (see Camps et al., Macromol Chem. Physics, C22(3), 343, 1982-83; Montheard et al., Rev. Macromol. Chem. Phys., (C-28, 503, 1988; and Chemical Modification of Polymers Via Phase Transfer Catalysis by J. M. J. Frechet in "Crown Ethers and Phase Transfer Catalysts in Polymer Science", edited by Matthews and Canecher and Published by Plenum Press, N.Y., 1984).
It is well-known that most of polyolefins are produced by coordination polymerization using transition metal catalysts, commonly known as Ziegler-Natta catalysts (see J. Boor, Jr., Ziegler-Natta Catalysts and Polymerizations; Academic Press: New York, 1979). In recent years, the new developments in metallocene homogeneous catalysts (see Kaminsky et al, U.S. Pat. No. 4,542,199; Ewen et al, U.S. Pat. No. 4,530,914; Slaugh et al, U.S. Pat. No. 4,665,047; Turner, U.S. Pat. No. 4,752,597; Canich et al, U.S. Pat. No. 5,026,798 and Lai et al, U.S. Pat. No. 5,272,236) provide a new era in polyolefin synthesis. With a well-defined (single-site) catalyst, monomer insertion can be effectively controlled. The reaction is especially important for copolymerization reactions. Several prior art disclosures have shown the use of metallocene catalysts with constrained ligand geometry producing linear low density polyethylene (LLDPE) with narrow composition distribution and narrow molecular weight distribution. The relatively opened active site in a metallocene catalyst provides equal access for both comonomers. The incorporation of olefin comonomer is significantly higher than those obtained from tranditional Ziegler-Natta catalysts. In addition, the prior art has identified the cationic coordination mechanism responsible for the polymerization reaction conducted in the presence of the single site catalysts. Both cationic active site insertion mechanism and effective copolymerization of comonomers are very important and favorable for the incorporation of para-alkylstyrene in polyolefins.
Although useful in many commercial applications, polyolefins, such as high density polyethylene (HDPE) and isotactic polypropylene (i-PP), suffer a major deficiency, i.e., poor interaction with other materials. The inert nature of polyolefins significantly limits their end uses, particularly, those in which adhesion, dyeability, paintability, printability or compatibility with other functional polymers is paramount. Unfortunately, polyolefins have been the most difficult materials in chemical modifications, both in functionalization and graft reactions. In post-polymerization, the inert nature and crystallinity of the polymer usually cause the material to be very difficult to chemically modify under mild reaction conditions. In many cases, the reaction involves serious side reactions, such as degradation in the polypropylene modification reaction. In the direct polymerization, only a Ziegler-Natta process can be used in the preparation of linear polyolefins. It is normally difficult to incorporate functional group-containing monomers into the polyolefins by Ziegler-Natta catalysts due to catalyst poisons (see J. Boor, Jr., Ziegler-Natta Catalysts and Polymerizations; Academic Press: New York, 1979). Our previous inventions (see Chung et al, U.S. Pat. No. 4,734,472; 4,751,276; 4,812,529; 4,877,846) have taught the uses of borane-containing polyolefins. The chemistry involves the direct polymerization by using organoborane-substituted monomers and .alpha.-olefins in Ziegler-Natta processes. The homo- and copolymers containing borane groups are very useful intermediates to prepare a series of functionalized polyolefins. Many new functionized polyolefins with various molecular architectures have been obtained based on this chemistry. In addition, it has been demonstrated that the polar groups can improve the adhesion of polyolefin to many substrates, such as metals and glass (see Chinsirikul et al, J. Thermoplastic Composite Materials 6, 18, 1993 and Lee et al, Polymer, 35, 2980, 1994). The chemistry of borane containing polymers has also been extended to the preparation of polyolefin graft copolymers, which involves free radical graft-from reaction (see Chung et al, U.S. Pat. No. 5,286,800, 1994). In polymer blends, the incompatible polymers can be improved by adding a suitable polyolefin graft copolymer which reduces the domain sizes and increases the interfacial interaction between domains (see Chung et al, Macromolecules 26, 3467, 1993; Macromolecules, 27, 1313, 1994).